The application claims priority to Chinese Application Serial No. 99114216.0, filed on May 19, 1999, and Chinese Application Serial No. 99114530.5, filed on Nov. 5, 1999.
The invention relates to the sunlight application technology, and in particular, to a sunlight tracking sensor and its use in a light collecting device which can follow the sun fully automatically.
Sunlight is an inexhaustible energy source in nature. However, so far the use of sunlight by mankind has remained basically at a primary stage of natural lighting, e.g. indoor lighting by using direct sunshine through windows or skylights. Nevertheless, for some dwellings in densified residential areas and buildings such as underground shopping centers, direct solar rays cannot radiate into the buildings at daytime. In fact, the effective collection and rational utilization of sunlight are of great significance and have good prospects. For example, the direct and effective collection and utilization of sunlight can not only be used as a common indoor lighting means, but also be used for lighting those places requiring illumination with higher safety, such as dangerous articles storage, coal mines, tunnels and underwater operation.
To achieve the above-mentioned goals, the existing solutions generally contain a sunlight focusing unit, a driving unit, a light-transmitting unit, feedback control circuits and sunlight tracking sensors. In order to collect sunlight with high efficiency, the sunlight collecting device should be made to follow the apparent movement of the sun and to be always aligned directly with the solar rays. To meet this need, various sunlight tracking sensors based on different operation principles have emerged. For example, Chinese patent CN95107312.5 under the name xe2x80x9cSunlight Collecting Device and Sunlight Collection Control Device for Controlling Such Collecting Devicexe2x80x9d, applied by Sanyo Electric Machinery Co. Ltd of Japan disclosed a light collecting device in which one or more light collection prisms are mounted in a collecting component at specified spaces and in a free-rotating manner, and a light collection control device comprising a solar position detector, a central processing device formed of an operation and a memory device such as a microprocessor and an optical axis sensor. The sunlight tracking device in this application detects the sun altitude using the optical axis sensor on the principle of imaging through an aperture and, after the processing by the central processing circuits, makes the light collecting device follow the sun automatically by means of the driving unit. However, the construction of the sensing, detecting and processing functions in this solution are complicated and costly, thus not widely used.
Another previous patent is Japanese Kokai Tokkyo Koho JP7-43599 under the name xe2x80x9cSunlight Tracking Sensorxe2x80x9d, the construction of which is as shown in FIG. 15. Sensors S are provided in a sunlight collecting device. One or more optical fibers FP with light-absorbing layer are provided on the whole light-receiving plane of such a sensor. The sunlight collecting device comprises an opaque cylinder A, and at the upper end of the cylinder A, there is an opaque circular cover B having a central hole. The sensors are disposed at the lower end of the cylinder A at symmetric positions equal to the inner diameter of the circular cover B.
The operating principle of these sensors and light collecting devices are illustrated in FIG. 16. L represents fictitious rays falling vertically from the hole edge of the opaque cover B down to the lower end of the cylinder A. Sunlight sensors S are disposed symmetrically along the circumference of these fictitious rays. The light signals received by each sensor S and the sensor at the corresponding position are processed by a circuit for comparison and amplification, and then the sunlight collecting device is driven to rotate to keep following the sun with high accuracy. This principle of detecting sunlight has a very obvious shortcoming. The device has only several light-receiving spots but not an all-directional light-receiving plane. Therefore, there must be blind zones in light receiving, and it is impossible to have all around, complete and accurate detection of sunlight. To sum up, the above-mentioned sensors have difficulty in making the light collecting device track the sun in all directions, thus resulting in less utilization of sunlight.
In view of the shortcomings of existing techniques, the present invention provides a sunlight tracking sensor, whose light sensing faces receive light signals in all directions, thus virtually eliminating blind zones in light receiving. In addition, the light sensing faces in each quadrant of the sensor can sense light signal components in the directions of two coordinate axes (FIG. 1), and after comparison and amplification of light signals by the circuits corresponding to the two groups of output ends, the light collecting device is driven to follow the sun correctly so that the accuracy of sunlight tracking is significantly increased.
The present invention also provides a sunlight collecting device which follows the sun fully automatically by using the above-mentioned sensor for collecting sunlight for illumination. By use of the high-accuracy sensor of this invention,. the sunlight collecting device is ensured to track sunlight with high accuracy and hence achieve higher sunlight utilization efficiency.